1. Field of the Invention
The present invention relates to a protection arrangement for optical transmitter and receiver devices.
2. Background Information
Such an arrangement is already known in the art, e.g. from the article "Decreasing survivable fibre network cost using optical switches" by Tsong-Ho Wu et al, Globecom 88, IEEE Global Telecommunications Conference and Exhibition, Hollywood, Fla., Nov. 28-Dec. 1, 1988, Volume 1, page 3.6.2 second paragraph. Therein, a so-called 1:p protection circuit means that p working circuits are protected by 1 spare circuit, i.e. when one of the working circuits is defective it is replaced by the spare one. In this article the protection arrangement includes a 1:3 electronic protection circuit and the latter protects a transmitter/receiver device which consists of three communication branches each comprising an optical transmitter and receiver circuit interconnected by an optical cable. The protection circuit includes a transmitter and a receiver circuit interconnected by an optical cable. Whenever one of the transmitter circuits or one of the receiver circuits of the transmitter/receiver device becomes defective the complete communication branch, i.e. the transmitter circuit, the receiver circuits, as well as the connecting optical cable, are bypassed by and replaced by the protection circuit.
A drawback of this known arrangement is that even when only one of either the receiver circuit or the transmitter circuit is defective, the other correctly working transmitter or receiver circuit, as well as the optical cable, are replaced together with the defective circuit.